/*
调用方法:var myDrag=new Endrag(source,target,offSetX, offSetY);
参数说明:source--鼠标动作绑定对象;target--操作目标对象(要移动的对象);offSetX--横坐标偏移;offSetY--纵坐标偏移
说明:通过多次调用本方法绑定多个对象的拖动
*/
 funs={
    index:100, 
    getFocus:function (target){ 
        if(target.style.zIndex!=this.index){ 
            this.index += 2; 
            var idx = this.index; 
            target.style.zIndex=idx; 
        } 
    },
    abs:function (element) {
        var result = { x: element.offsetLeft, y: element.offsetTop};
        element = element.offsetParent;
        while (element) {
            result.x += element.offsetLeft;
            result.y += element.offsetTop;
            element = element.offsetParent;
        }
        return result;
    }
 };
 
 function Endrag(source,target,offSetX, offSetY){
    source=typeof(source)=="object" ? source:document.getElementById(source);
    target=typeof(target)=="object" ? target:document.getElementById(target);
    var x0=0,y0=0,x1=0,y1=0,moveable=false,index=100,NS=(navigator.appName=='Netscape');
    offSetX=typeof offSetX== "undefined" ? 0:offSetX;
    offSetY=typeof offSetY== "undefined" ? 0:offSetY;
    source.onmousedown=function(e){
        e = e ? e : (window.event ? window.event : null);
        funs.getFocus(target);
        if(e.button==(NS)?0 :1)  {
            if(!NS){this.setCapture()}
            x0 = e.clientX ; 
            y0 = e.clientY ; 
            x1 = parseInt(funs.abs(target).x); 
            y1 = parseInt(funs.abs(target).y);   
            moveable = true; 
        } 
    }; 
    //拖动; 
    source.onmousemove=function(e){
        e = e ? e : (window.event ? window.event : null); 
        if(moveable){ 
            target.style.left = (x1 + e.clientX - x0 - offSetX) + "px"; 
            target.style.top  = (y1 + e.clientY - y0 - offSetY) + "px"; 
        } 
    };
    //停止拖动; 
    source.onmouseup=function (e){
        if(moveable)  {  
            if(!NS){this.releaseCapture();}
            moveable = false; 
        } 
    };
}